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An analysis of genetic data from 29 Native American populations supports a single main migration across the Bering Strait 12,000 years ago and suggests that a Siberian origin to Native Americans is more likely than a South Asian or Polynesian origin.

University of Michigan scientists and a group of geneticists and anthropologists examined genetic variation at 678 key locations or markers in the DNA of present-day members of 29 Native American populations across North, Central and South America. They also analyzed data from two Siberian groups.

The group’s findings were published online in PLoS Genetics.

The analysis showed:

Genetic diversity, as well as genetic similarity to the Siberian groups, decreases the farther a native population is from the Bering Strait — adding to existing archaeological and genetic evidence that the ancestors of native North and South Americans came by the northwest route.

A unique genetic variant is widespread in Native Americans across both American continents — suggesting that the first humans in the Americas came in a single migration or multiple waves from a single source, not in waves of migrations from different sources. The variant, which is not part of a gene and has no biological function, has not been found in genetic studies of people elsewhere in the world except eastern Siberia.

The researchers said the variant likely occurred just prior to migration to the Americas, or immediately afterwards.

“We have reasonably clear genetic evidence that the most likely candidate for the source of Native American populations is somewhere in east Asia,” said Noah A. Rosenberg, Ph.D., assistant professor of human genetics at the UM Medical School.

“If there were a large number of migrations, and most of the source groups didn’t have the variant, then we would not see the widespread presence of the mutation in the Americas,” he said.

Rosenberg previously studied the same set of 678 genetic markers used in the new study in 50 populations around the world, to learn which populations are genetically similar and what migration patterns might explain the similarities. For North and South America, the current research examines a large number of native populations using a large number of markers.

The pattern the research uncovered — that as the founding populations moved south from the Bering Strait, genetic diversity declined — is what one would expect when migration is relatively recent, according to Mattias Jakobsson, a post-doctoral fellow in human genetics at the UM Medical School. It is believed there has not been time yet for mutations that typically occur over longer periods to diversify the gene pool.

The study’s findings hint at supporting evidence for scholars who believe early inhabitants followed the coasts to spread south into South America, rather than moving in waves across the interior.

“Assuming a migration route along the coast provides a slightly better fit with the pattern we see in genetic diversity,” said Rosenberg.

The study also found that:

Populations in the Andes and Central America showed genetic similarities.

Populations from western South America showed more genetic variation than populations from eastern South America.

Among closely related populations, the ones more similar linguistically were also more similar genetically.